Compelling evidence has been presented that immunobiological interactions are very important in development and prevention of the two major oral diseases, i.e., periodontal disease and dental caries. For example, polyclonal and antigen-specific immune responses to periodontopathoges, e.g., Bacteroides gingivalis (Bg) and Haemophilis actinomycetemcomitans (Ha) play important roles in the development of gingival tissue destruction in periodontal diseases. It has also been shown that oral administration of Streptococcus mutans vaccine to human induces antigen-specific secretory IgA (S-IgA) responses in mucosal associated secretions including saliva, tears, colostrum and mucus secretions of the gastrointestinal and upper respiratory tracts, and that antigen-specific IgA producing cell appear in the peripheral circulation prior to IgA responses in these external secretions presumably as a part of the common mucosal immune system. However, very little is known about regulatory mechanisms, especially T cell involvement in these immune responses. In this regard, the overall goal of this grant proposal is to study the cellular and molecular aspects of T cell regulation of immune responses in both periodontal disease and caries immunity. Regulatory T cell populations from gingival of periodontal disease patients or peripheral blood mononuclear cells of orally-immunized human subjects will be isolated and characterized for their phenotype (e.g., Leu 1, Leu 4, Leu 3a and Leu 2a) and for Fc receptor expression (e.g., Fc alpha R, Fc gamma R and Fc mu R). Furthermore, purified subsets of T cells will be cloned and hybridoma lines generated for analysis of isotype-specific helper and suppressor function in B cell proliferation, differentiation and Ig synthesis. Special attention will be given to lymphokine analysis including IL 2, IL 4 and Il 5, and especially isotype specific lymphokines (e.g., FcR and immunoglobulin binding factors). Isotype-specific lymphokines will be extensively characterized using modern molecular biology techniques. We will construct cDNA libraries with the gamma gtll system, by in vitro transcription and translation using the pSP64 system and by use of oligonucleotide probes for the analysis of isotype-specific regulatory T cell molecules. This grant proposal represents a comprehensive molecular and cellular analysis of isotype-specific regulatory T cells which are involved in both human periodontal disease and caries immunity.